Combined aircrew systems tester (CAST)

ABSTRACT

The present invention enables functional testing nearly all aircrew equipment including a COMBAT EDGE (combined advanced technology enhanced design “G” ensemble) system components which include a mask, a G-suit, communication systems, and a goggle. The present invention includes a gas system which includes an input filter, a first compressor comprising at least one blower, preferably three blowers connected in series, a second compressor, a first flow sensor a second flow sensor, a first flow valve, a second flow valve, a regulator, a first pressure sensor, a second pressure sensor, a first pressure valve, a second pressure valve, and a controller. The inlet filter designed to accept a chemical filter. The second compressor produces a lower flow at a higher pressure than the first compressor. This combination works particularly well when inflating the G-suit because when the G-suit inflates, initially there is a large change in volume without much change in pressure, and then, as the G-suit fills out and becomes firm, the change in volume slows down and the rate of the pressure increases. The present invention includes a digital indicator. A method of operating the tester and the gas system are also disclosed. The present invention includes a normal breathing test, a preflight test, a fit test, a G-suit leak test and two dynamic flow leak tests. The communication system test and the goggle test are further included.

CLAIM OF PRIORITY

This application makes reference to, incorporates the same herein, andclaims all benefits accruing under 35 U.S.C. §119 from a provisionalapplication entitled Combined Aircrew Systems Tester (CAST) filed in theUnited States Patent & Trademark Office on 1 Aug. 2001, and there dulyassigned Ser. No. 60/308,846 by that Office.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a combined aircrew systems tester, andmore particularly, to a combined aircrew systems tester enablingfunctional testing of aircrew equipment.

2. Description of the Background Art

Life support systems are very crucial for members of an aircrew ofaircraft and especially high performance aircraft. Life support systemsinclude COMBAT EDGE (combined advanced technology enhanced designG-ensemble) system components. The system includes a G-suit, an oxygenmask, goggles, and a communication equipment. Specifically, the COMBATEDGE system includes the MBU-20/P Oxygen Mask, CSU-17/P Vest Assembly,HGU-55/P Helmet with occipital bladder, CRU-94/P Integrated TerminalBlock or PBG (pressure breathing for Gs) Chest Mounted Regulator or bothCRU-94/P Integrated Terminal Block and PBG Chest Mounted Regulator, andall associated Anti-G garments.

Life support systems are very important for the aircrew and therefore,it is extremely important that such vital systems be properly tested. Ifany of the above systems do not work, a pilot for instance may be unableto control the aircraft.

Earlier systems had different testing units for each type of lifesupport. A separate cumbersome unit would be needed for testing anoxygen mask and another separate large unit would be needed for testingthe anti-G suit. This is expensive and very awkward for users to testtheir equipment at different stations while for instance they arewearing such equipment. Moreover, the power sources for such equipmentare usually not commonly available because of the high power necessaryto drive such complicated devices.

Particularly, a conventional tester for an oxygen mask requires aseparate high pressure source of breathing air/oxygen. It is awkward forusers to bring the tester and the separate high pressure source.

For the foregoing reasons, there is a need for a tester that can beinexpensively and efficiently test life support equipment.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to have an integratedunit that can functionally test the various aircrew equipment.

It is another object to have an aircrew systems tester that can test allof the aircrew life support equipment and communication systems.

It is yet another object to have a unit that can test the aircrew lifesupport equipment and yet not require much power for operation.

It is still yet another object to have a unit that tests the aircrewlife support equipment and yet not require high pressure air/oxygencylinders.

It is still another object to have a unit that tests the aircrew lifesupport equipment and significantly reduces supporting man hours,deployment costs and mobility footprint.

It is still further object to have a life support system tester that isable to operate in a chemical warfare environment.

To achieve the objectives of the present invention, there is provided atester including a gas system which includes an input filter located inan inlet port, the input filter filtering an air to prevent foreignparticles from entering the gas system, a first compressor compressingthe air, the first compressor comprising at least one blower, a speed ofthe blower depending on a voltage applied to the blower, a secondcompressor compressing the air, the second compressor producing a lowerflow than the first compressor, the second compressor producing a higherpressure than the first compressor, a first flow sensor detecting a flowof the compressed air and a leaking of the aircrew systems, a secondflow sensor detecting the flow of the compressed air and the leaking ofthe aircrew systems, a first flow valve mounted for controlling the flowof the compressed air to the first flow sensor, a second flow valvemounted for controlling the flow of the compressed air to the secondflow sensor, a regulator regulating a pressure of the second system, afirst pressure sensor detecting a pressure of the mask, a secondpressure sensor detecting the pressure of the second system, a firstpressure valve for controlling the pressure of the first system, asecond pressure valve for controlling the pressure of the second system,and a controller controlling an operation of the gas system. The inletfilter designed to accept a C2 (chernical) filter. The gas system isparticularly suitable for testing a mask and a G-suit. It is preferredthat the first compressor comprises three regenerative blowers, a firstblower, a second blower, and a third blower, connected in series. It ispreferred that each of the three regenerative blowers has 21 inch H₂O ofa maximum output pressure. In a preferred embodiment, the firstcompressor compresses the air until a G-suit pressure reaches 55 inchH₂O, the second compressor starts to compress the air when the G-suitpressure is about 55 inch H₂O and finishes when the G-suit pressure isabout 70 inch H₂O. The first flow sensor is able to measure the flowfrom 0 to 10,000 cc/min (cubic centimeters per minute), and the secondflow sensor is able to measure the flow 0 to 300 cc/min. The first flowvalve and the second flow valve determine which sensor is used. The gassystem further includes a digital indicator reading out data outputtedfrom the first and second flow sensors. The gas system further includesa first limit valve for limiting a pressure of the first system. Theoperation of the gas system is controlled by a main printed circuitboard (PCB) which uses CMOS (complementary metal oxide semiconductor)logic. The present invention further includes a speed control printedcircuit board (PCB) which controls the first compressor by controlling avoltage applied to the first compressor.

The tester of the present invention includes a first unit for testing amask, a second unit for testing a G-suit, and a third unit for testing acommunication system. The tester can further includes a fourth unit fortesting a goggle. Since the tester of the present invention is selfcontained and integrated, a control panel of the tester of the presentinvention has a plurality of switches and indicators for controlling thetests for the life support systems of an aircrew member. The third unitpreferably includes an input accommodating a microphone, an inputaccommodating headset, and two inputs for carbon microphones. The thirdunit further includes a built-in continuity tester. The third unit canfurther includes an accommodation of a second headset and microphoneaccommodating a first user to communicate with a second user.

A method of operating a gas system for testing aircrew systems whichincludes a mask and a G-suit is comprised of the steps of selecting atest mode between the test mode for the normal breathing and the testmode for the PBG breathing, filtering an ambient air with a C2 filter,compressing the air, detecting a flow of the air, and detecting apressure of the mask or G-suit. When the mask test mode is selected, thestep of compressing the air further includes the step of turning on thefirst compressor. When the PBG mode test is selected, the step ofcompressing the air further includes the steps of turning on the firstcompressor until a G-suit pressure reaches 55 inch H₂O, turning off thefirst compressor and turning on the second compressor when the G-suitpressure is about 55 inch H₂O, and turning off the second compressorwhen the G-suit pressure is about 70 inch H₂O. The first compressor iscontrolled by adjusting a voltage applied to each of the first, second,and third blowers and by deciding how many blowers are turned on.

With this configuration, the present invention enables functionaltesting of nearly all aircrew equipment including the COMBAT EDGE(Combined Advanced Technology Enhanced Design “G” Ensemble) systemcomponents.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of this invention, and many of theattendant advantages thereof, will be readily apparent as the samebecomes better understood by reference to the following detaileddescription when considered in conjunction with the accompanyingdrawings in which like reference symbols indicate the same or similarcomponents, wherein:

FIG. 1 illustrates a functional diagram of a gas system of the presentinvention;

FIG. 2 illustrates the control panel of the present invention;

FIG. 3 illustrates an overall block diagram of the present invention;

FIGS. 4A through 4S illustrate schematic diagrams of sections 4A through4S, respectively of FIG. 3 of the present invention; and

FIG. 5 illustrates a general block diagram of a portion of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is an integrated unit that can functionally testthe various aircrew equipment. Life support systems include COMBAT EDGE(combined advanced technology enhanced design G-ensemble) systemcomponents. The system includes the MBU-20/P Oxygen Mask, CSU-17/P VestAssembly, HGU-55/P Helmet with occipital bladder, CRU-94/P IntegratedTerminal Block or PBG (pressure breathing for Gs) Chest MountedRegulator or both CRU-94/P Integrated Terminal Block and PBG ChestMounted Regulator, and all associated Anti-G garments.

A functional diagram of a gas system for a combined aircrew systemtester (CAST) is shown in FIG. 1.

The gas system of the tester provides two air sources. One is for a maskor a vest, and the other is for a G-suit (a suit designed to counteractthe physiological effects of acceleration on an aviator orastronaut—called also called an anti-G suit). The air for the G-suit isprovide through a G-suit port and the air for the mask/vest through themask port. These air sources are used to perform maintenance andpreflight testing of the pilot's life support equipment. The mask portair is used to test the pilot's oxygen mask and COMBAT EDGE gear. Thereare two modes of mask testing, ‘normal’ and ‘PBG’ (Pressure Breathingfor G (acceleration force of gravity)).

Referring to FIGS. 1 through 4, air for the mask starts by passingthrough an input filter 101. The ambient air is inputted through aninlet port. A screen mesh filter assembly screws into the inlet port toprevent particles from entering the air stream. The thread on the inletport is designed so that it can accept a C2 (chemical) filter 246 usedfor chemical warfare. This feature makes it possible to use the testerin a chemical environment. All the air outputted by the tester passesthrough the C2 when it is installed.

Then, the air for the mask is compressed by a low-pressure compressorsystem 102.

The low-pressure compressor system 102 includes at least one blower butpreferably includes at least three regenerative blowers 102 a, 102 b and102 c connected in series to generate the necessary pressure and flow.The output pressure is determined by the speed of the blowers 102 a, 102b and 102 c and how many blowers 102 a, 102 b and 102 c are turned on.The voltage applied to each of the blowers 102 a, 102 b and 102 ccontrols the speed. If the voltage decreases, the speed decreases andthe output pressure is decreased. The voltage is controlled by a speedcontrol circuit, which is part of the speed control PCB (Printed CircuitBoard, PCB3).

Then, the air for the mask passes through one of two flow sensors 106,107, which are used to alert the user that his or her equipment isleaking and to measure the leak rate. One flow sensor is a high flowsensor 106 which measures flow from 0 to 10,000 cc/min (cubiccentimeters per minute) and the other flow sensor is a low flow sensor107 which measures flow from 0 to 300 cc/min. A mask control valve 104and a low flow valve 105 determine which sensor is used. One of twovalves 104 and 105 which are normally closed is open to permit the airto flow through one of the flow sensors 106 and 107. The output from theflow sensor 106 or 107 is fed into a digital indicator 274 (FIG. 2) toindicate flow. The indicator 274 reads out in the appropriate units. Itsrange is set by an embedded processor on a main PCB (Printed CircuitBoard, PCB1).

These sensors are excited with 10.0 VDC (voltage of direct current). Atzero flow their output is 1.0 VDC (voltage of direct current). At fullscale the output is 5.0 VDC (voltage of direct current). The low flowsensor 107 is not quite linear. To compensate for this, five linearcurves are fitted to the flow versus voltage curve. The slopes of thesefive curves are programmed into the digital indicator 274 that is usedto indicate flow.

Next, the air passes through a check valve 118 and flows out the maskport 242. The check valve 118 prevents foreign materials from enteringthe gas system of the tester. A pressure switch 111 and a mask pressuresensor 112 monitor the mask port pressure. They are used to control andlimit the mask port pressure. The mask pressure sensor 112 convertspressure to voltage. The voltage is fed into the digital indicator 270where it is converted to a digital signal, which is presented as numberscaled in engineering units. This number is updated 13 times a second.The indicator has three logic high outputs, which output when thepressure exceeds their set pressure. In addition, the pressure switch111 is connected to the mask pressure sensor 112. The pressure switch111 is normally closed, and is preferably set to open at 18 in (inch)H₂O.

A mask limit valve 114 and a backup mask limit valve 115 are alsoprovided for controlling the mask port pressure.

The air for the G-suit is produced by multiple compressors 102 a, 102 b,102 c and 103. At pressures below 55 in H₂O, the low-pressure compressorsystem 102 compress the air. At pressures above 55 in H₂O, ahigh-pressure compressor 103 compresses the air. This is done tominimize the amount of time to inflate the G-suit. The low-pressurecompressors (with regenerative blowers) 102 a, 102 b and 102 c producehigh flow at relatively low pressures while the high-pressure compressor103 produces low flow but can compress the air to a higher pressure.This combination works particularly well when inflating the G-suitbecause when the G-suit inflates, initially there is a large change involume without much change in pressure, and then, as the G-suit fillsout and becomes firm, the change in volume slows down and the rate thepressure increases.

A G-suit regulator enable valve 109 and a G-suit regulator 108 areprovided for regulating the G-suit pressure. The G-suit regulator enablevalve 109 is normally closed. When the G-suit pressure increases up to acertain pressure, the G-suit regulator enable valve 109 is opened tovent the G-suit regulator 108.

A G-suit control valve 110 is further provided for controlling theG-suit pressure.

With this configuration, the present invention does not require aseparate high pressure source of breathing air and oxygen.

As explained above, the present invention is self contained. Thus, acontrol panel of the combined aircrew systems tester of the presentinvention has a plurality of switches and indicators for controlling thetests for the life support systems of an aircrew member.

FIG. 2 shows a preferred embodiment of the control panel.

As shown in FIG. 2, the control panel 200 includes a ‘mode select’switch 201, a ‘pressure select’ switch 202, a ‘test select’ switch 203,and a ‘press to test’ switch 204.

The mode select portion 201 includes a mode select switch 201Apreferably provides for two dynamic flow leak testing (high leak(‘LK-HI’) 201D and low leak (‘LK-LO’) 201C), a G-suit leak testing(‘LK-GS’) 201B, and one mask testing (‘mask’) 201E.

The pressure select switch 202 is preferably provided for 41M, 43M, or45M (where M stands for 1000). Thus, the air is provided at one of fourpositive pressures; normal, 41M, 43M, or 45M.

The test select switch 203 provides for a PBG breathing testing (‘PBG’),a normal breathing testing (‘normal’), and ‘off’. The test select switch203 is preferably a three-position toggle switch. The test select switch203 drives two de-bouncers 332, 334, the PBG and the normal logic steps.

A leaking indicator 235 is also included in the control panel 200.

The communication section includes audio input A 222 and B 224, a carbonheadset input 226, a press to test (‘PTT’) jack 228, a continuity statusof a microphone 230, a continuity status of the earphone 232, amicrophone “on” indicator 234, an audio select switch 236 that can beswitched to continuity test mode 236 a, ‘LIS/TLK 1’ (listen/talk 1) 236b, or ‘LIS/TLK 2’ 236 c. A port for the goggle 238 and a ‘G-suit’ button240 are included along with a mask port 242. Indicators 244 a and 244 brelating to the PBG(pressure breathing for Gs) are also included.Reference 244 b indicates that ‘PBG timed out’, 244 a indicator concernsthe ‘PBG’. The control panel 200 also includes the filter 246. There areports for the power 248 and the battery 250. A switch or indicator fortare 252 is along with a hold 254, and a reset 256 indicator or switch.A G-suit ready indicator 258 is also included along with a G-suittesting 260 and a pressure control knob 262. The tester also includes aG-suit port pressure displays 268, a mask port pressure display 270, atime display 272, and a high and low flow display 274. The displays canbe a digital display such as light emitting diodes, or liquid crystaldisplay or other types of indicators.

The operation of the tester is explained in more details as follows.

To test the mask when the aircrew does not wear COMBAT EDGE, the userselects a mask mode of operation by pressing the mode select switch 201.The user selects a desired breathing pressure by pressing the pressureselect switch 202. Then the test select switch 203 is toggled to the‘normal’ position, which starts air flow out of the mask port at slightpositive pressure. Then the press to test button 204 is pushed to causethe air pressure to increase to the pressure selected. The air ispreferably provided at one of four positive pressures; normal, 41M, 43M,or 45M. When the mask mode has been selected and the test select switchis in the ‘normal’ position, the mask control valve 104 opens permittingthe air to flow out the mask port. When operating in the normal maskmode, the air outputted through the mask port is provided at a pressurefrom 1 to 10 in H₂O.

The PBG (Pressure breathing for G) breathing is used to performpreflight tests and fit tests while the users are wearing COMBAT EDGE.The users wearing COMBAT EDGE are required to take the preflight test ontheir masks at PBG breathing pressure level. This test is performed at abreathing pressure of 16 in H₂O with the G-suit not inflated. When theG-suit is not inflated, it is dangerous to breathe air at pressures muchabove 16 in H₂O. When the mode select switch 201 is set to ‘mask’ andthe test select switch 203 is in the ‘PBG’ position, the air flows frommask port at normal pressure. When the press to test button 204 isdepressed, the breathing pressure increases to 16 in H₂O. The userverifies that he or she is breathing normally, verifies proper maskfunctions and notes that their vest starts to inflate. Then the usermomentarily stops breathing to test a leak. A light of the leakingindicator 235 will go out if there are no leaks greater than 5.5 lpm(liters per minute). When the press to test button 204 is pressed, thespeed of the low-pressure compressor system 102 increases.

After a user is initially fitted with COMBAT EDGE equipment, a fit testis performed. This test is similar to the preflight test except the fittest is performed at 32 in H₂O. The user has to be sitting down toperform this test. The fit test starts by performing the preflight test.Then the mask port pressure is increased slowly to 32 in H₂O byadjusting the pressure control release and knob 262 until the airpressure reaches 32 in H₂O. Then the preflight test is repeated.

During preflight and fitting a red light turns on when flow exceeds 5.5lpm. The user momentarily holds his or her breath to check for leaks. Ifthere are no leaks, the leak light is turned off.

The voltage from the low flow sensor 107 is compared with a presetvoltage that is equivalent to the sensor output when the flow is 5.5lpm. When the voltage exceeds the preset voltage, the light of theleaking indicator 235 is turned on.

In order to do the preflight test safely, the G-suit has to be inflated.The low-pressure compressor system 102 and the high-pressure compressor103 provide the air for the G-suit. When the G-suit switch 260 is turnedon, the G-suit control valve 110 opens and the low-pressure compressorsystem 102 is turned on at its maximum operating speed so that the airrapidly fills the G-suit to its final approximate shape. When the G-suitpressure reaches 55 in H₂O, as sensed by G-suit pressure sensor 113, thehigh-pressure compressor 103 takes over filling the G-suit to its finalpressure. The output of the G-suit pressure sensor 113 is fed into thedigital indicator/controller 268. The indicator 268 turns the inputvoltage into a digital signal and processes it, rescaling it intoengineering units and outputting it in the form of a number presented onthe indicator. The G-suit pressure is maintained at 60 in H₂O by theG-suit regulator 108. If the G-suit pressure exceeds 70 in H₂O, thehigh-pressure compressor 103 is turned off to limit the G-suit pressureto 70 in H₂O. After the G-suit pressure stabilizes at 60 in H₂O, theuser turns off the G-suit switch 260.

The G-suit is periodically checked for leakage. To do this, the G-suitis pressurized to 138.4 in H₂O (5 psi, pounds per square inch) andmonitored for a change in pressure over an interval of time.

When the mode select switch 201 is in ‘LK-GS’ and the G-suit switch 260is turned on, the G-suit regulator enable valve 109 is turned on todisable the G-suit regulator 108, allowing the G-suit pressure to riseto pressures greater than 60 in H₂O, which is a normal G-suit operatingpressure. The high-pressure compressor is turned off at 138.4 in H₂O.When the pressure reaches 138.4 in H₂O, the power to the G-suit controlvalve 110 and the high-pressure compressor 103 is turned off to limitthe pressure to 138.4 in H₂O. Once the pressure stabilizes, the userturns off the G-suit switch 260 to close off the G-suit. The tare switch252 is pushed for zeroing the time and G-suit pressure. At 120 secondsthe hold button 254 is pressed for holding the indicated change in timeand change in G-suit pressure. From these changes, the leak rate can beobtained.

When the mode select switch 201 is in the ‘LK-HI’ position (indicator201D), the mask control valve 104 is opened. The low flow valve 105remains off for directing all the flow through the high flow sensor 106.

When the mode select switch 201 is in the ‘LK-LO’ position (indicator201C), the mask control valve 104 is closed. The low flow valve 105 isturned on for directing all the flow through the low flow sensor 107.

A second method used to verify the oxygen equipment seals is to measurea drop in pressure over an interval of time. The component under thetest is attached to the mask port and is pressurized to 32 in H₂O bysetting the mode to ‘mask’ and the test select switch 203 to ‘PBG’. Thepress to test button 204 is pushed and the pressure control knob 262 isadjusted until air pressure reaches 32 in H₂O. After the pressure hasstabilized, the press to test button 204 is released to cut off the airsource. The tare switch 252 is pressed to start a timer and zero thepressure indicator, 268 and 270. At a prescribed time the hold switch254 is pressed to hold the timer and the pressure indicator readings. Ifthe change in pressure is less than a prescribed amount in theprescribed time, the leak rate is within tolerance.

The present invention is designed to address safety issues with thefollowing features.

When performing COMBAT EDGE testing, it is necessary to expose the userto excessive breathing pressures. Exposure to excessive breathingpressure can hurt the user. It is only safe under curtain conditions andfor limited periods of exposure. Under no circumstance should thebreathing air pressure exceed 34 in H₂O.

The present invention compresses the filtered ambient air to pressuresclose to the maximum allowable output mask pressure, while theconventional testers start with air that is compressed to pressures thatare orders of magnitude greater than the maximum allowable output maskpressure. If the step down regulation system in the conventionalpressures completely fails, the user is exposed to pressures that manytimes greater than what is safe. On the other hand, the user of thepresent invention would be exposed to pressures not higher than themaximum allowable mask output pressure.

As stated before, the blowers 102 a, 102 b, and 102 c provide thebreathing air. The maximum pressure that can be developed by each of theblowers 102 a, 102 b, and 102 c is 21 in H₂O when being driven by mainpower supply voltage at zero flow. If all pressure limiting systems wereto fail, the maximum breathing pressure that could be developed to 63 inH₂O at zero flow, which is comparable to the maximum safe pressure of 34in H₂O. When the user is breathing, the pressure is significantly less.

Another safety feature of the present invention is a mask pressurelimiting system. In the preflight test, if the pressure increases above18 in H₂O, the power to the mask limit valve 114 is cut, venting thesystem through a check valve 119. This check valve 119 prevents backflow through the mask limit valve 114 when the user is inhaling. Inaddition, the mask port pressure is limited to 34 in H₂O under allcircumstances. The backup mask limit valve 115 operating current ispassed through a pressure limit switch 111 set to open at 34 in H₂O. Thebackup mask limit valve 115 is a normally open valve. When the pressurelimit switch 111 opens, the operating current is interrupted to open thebackup mask limit valve 115.

The method of controlling the CAST is described in more detail below.FIGS. 4A through 4S illustrate schematic diagrams of sections 4A through4S, respectively of the overall block diagram of FIG. 3 of the presentinvention. The schematics of 4A through 4S are sectioned to show theentire schematic of the present invention. Some portions may overlap inorder to accurately show the connections between the individualelements.

The operation of the gas system is controlled by the main printedcircuit board (PCB 1), which uses CMOS (complementary metal oxidesemiconductor) logic to control the overall operation. There are twopressure sensors, two digital indicators, five switches and onepotentiometer that input and drive the logic functions located on themain PCB (Printed Circuit Board, PCB1). The logic outputs control thespeed control PCB (PCB3), and the valves that control flow.

All logic inputs are derived from either switch closures or TTL(transistor-transistor logic) located in the digital indicators. Theypass through de-bouncers. The de-bouncers clean up these inputs andturning them into single pulse square waves with CMOS logic high levels.

The outputs refer to either compressor motors or valves. The valveoutputs and the high-pressure compressor output are located on the mainPCB (PCB1). They include an opto isolator and power relays. This is doneto protect the CMOS logic from inductive spikes that occur whenswitching a valve. The high-pressure compressor output is located on themain PCB (PCB1) and the low-pressure compressors outputs are located onthe speed control PCB (PCB3).

A mode select circuit includes the mode select switch 201, a momentarypush button driving a Johnson Counter (also known as a twisted-ringcounter) (see FIG. 4D). The Johnson counter provides the ‘MASK’ for themask testing, ‘LK-HI’ for the high-leak testing, ‘LK-LO’ for the lowleak testing, and ‘LK-GS’ for G-suit leak testing. It drives fourbuffers, which drive four LEDs (light emitting diodes) 201B, 201C, 201D,201E, which indicate the mode that is selected. The pressure selectcircuit works the same way.

The test select circuit starts with a three-position toggle switch 203,which drive two de-bouncers. The de-bouncer outputs are the ‘PBG’ and‘normal’ logic steps. (See FIG. 4F)

The press to test switch 204 and the G-suit switch 260 drive twode-bouncers. Their outputs are the ‘TST’ and “GSUIT’ logic steps.

With respect to the G-suit pressure sensor 113 and the mask pressuresensor 112, the output from the G-suit pressure sensor 113 is fed into adigital indicator 268. The indicator 268 turns the input voltage into adigital signal and processes it, resealing it into engineering units andoutputting it in the form of a number presented on the indicator 268. Italso provides a TTL logic high output at 55, 70 and 138.4 in H₂O. Theindicator provides 10-volt excitation for the pressure transducer. Themask transducer (sensor) 112 works the same except it outputs TTL logichigh outputs at 1, 18 and 34 in H₂O. (See FIG. 4, part O)

The G-suit regulator enable valve 109 is normally closed. It is turnedon to vent the G-suit regulator 108 to regulate the G-suit pressure(GSP) to 60 in H₂O, which is the normal suit operating pressure. It isturned off when performing a G-suit leak test (LK-GS).

The G-suit control valve 110 is normally closed. In any mode selectposition other than ‘LK-GS’, the G-suit control valve 110 is turned onuntil the G-suit pressure reaches 70 in H₂O. In the ‘LK-GS’ position,the G-suit control valve 110 is turned on until the G-suit pressurereaches 138.4 in H₂O.

With respect to the low flow valve 105, this valve 105 is turned onuntil the mask pressure (MP) reaches 34 in H₂O when the press to testswitch 204 is pressed in the ‘LK-LO’ position

The mask limit valve 114 is normally open. When the test select switch203 is in ‘normal’, the mask limit valve 114 is closed when the MP (maskpressure) is less than 18 in H₂O. In the ‘LK-HI’ or ‘LK-LO’ or the testselect in the ‘PBG’ position, the mask limit valve 114 is on until maskport pressure reaches 34 in H₂O.

The mask control valve 104 is normally closed. In the ‘LK-HI’ position,the mask control valve 104 is on until the mask pressure reaches 34 inH₂O. In the ‘mask’ position, the mask control valve 104 is on when thetest select switch 203 is in the ‘PBG’ or ‘normal’ positions.

The backup mask limit valve 115 is normally open. It is closed at thesame time the mask limit valve 114 is closed. Its power passes throughthe pressure switch 111. If the mask pressure exceeds 34 in H₂O, thepressure switch 111 opens to cut off power to the backup mask limitvalve 115. The backup mask limit valve 115 opens to reduce the mask portpressure.

The ‘High-Pressure Compressor’ output turns on the high-pressurecompressor 103 at 55 in H₂O and off at 70 or 138.4 in H₂O. In the‘LK-GS’ position, it turns off at 138.4 in H₂O.

The ‘Low-Pressure Compressor 1’ output turns on the low-pressurecompressor 1 102 a when the test select switch 203 is in either the PBGor ‘normal’ positions. If the mode select switch 201 is in the ‘LK-HI’or ‘LK-LO’ position, the blower 102 a is on. This is done to providepositive flow whenever the mask port is in use.

The ‘Low-pressure Compressor 2’ output and the ‘Low-Pressure Compressor3’ output turn on the low-pressure compressor 2 as ‘102 b’ in FIG. 1 andthe low-pressure compressor 3 as ‘102 c’ in FIG. 1 when the test selectswitch 203 is in the ‘normal’ or ‘PBG’ position and the mask pressuredrops below 1 in H₂O. When the test switch 203 is in the ‘normal’ andthe mode select switch is ‘LK-LO’ or ‘LK-HI’ position, the low-pressurecompressor 2 and 3 102 b and 102 c are turned on when the press to testswitch 204 is pushed. When the test switch 203 is in the ‘PBG’, thelow-pressure compressor 2 and 3 102 b and 102 c are turned on when thepress to test switch 204 is pushed and, after one minute, these twolow-pressure compressors 102 b and 102 c are turned off.

The ‘Full ON’ output is used to turn on the three low-pressurecompressors 102 a, 102 b, and 102 c of the low-pressure compressorsystem 102 at their maximum operating speed when they are used toinflate the G-suit. This output is high when the G-suit switch 260 isturned on if no output is required from the mask port. The ‘Mask Port’output takes precedence over G-suit inflation.

If the ‘Variable Speed Enable’, ‘41 M Speed Enable’, ‘43M Speed Enable’or ‘45M Speed Enable’ is not turned on, the ‘Normal Speed Enable’ is on(high).

When 41 M is selected, the press to test button 204 is pushed, and thetest select switch 203 is in the ‘normal’ or ‘PBG’ position, the ‘41 MSpeed Enable’ is on (high).

When 43M is selected, the press to test button 204 is pushed, and thetest select switch 203 is in the ‘normal’ or ‘PBG’ position, the ‘43MSpeed Enable’ is on (high).

When 45M is selected, the press to test button 204 is pushed, and thetest select switch 203 is in the ‘normal’ or ‘PBG’ position, the ‘45MSpeed Enable’ is on (high).

When ‘LK-HI’ or ‘LK-LO’ or ‘PBG’ with the press to test button 204 ispushed, the ‘Variable Speed Enable’ is on provided the G-suit pressureis greater than 55 in H₂O. The output from the G-suit pressuretransducer (sensor) 113 is compared with a preset level to determinewhether condition is being met.

The high-pressure compressor is turned on by the ‘HP CMPR ON’ signal.The ‘HP CMPR ON’ goes high when the G-suit switch is turned on and thefollowing conditions are met; the G-suit pressure is greater than 55 inH₂O but less than 138.4 in H₂O, and the G-suit pressure is less than 70in H₂O or ‘LK-GS’ mode selected.

The speed control PCB (PCB3) provides power to the three low-pressurecompressors 102 a, 102 b and 102 c. The power provided to thelow-pressure compressors voltage is variable. This is done to vary thecompressors output pressure. The low-pressure compressor 1 102 a isturned off and on independently of the low-pressure compressors 2 102 band 3 102 c. The speed control section outputs one of four fixedvoltages or a variable voltage to the compressors that are turned on.Three adjustable voltage regulators tied in parallel supply thecompressor voltage. Five external variable resistors set the regulatorsoutput voltage. (See FIG. 4N)

The speed control PCB (PCB3) has eight logic inputs. The logic inputsset the variable speed control and determine which compressors areturned on. The logic inputs are ‘Full On’, ‘the Low-Pressure Compressor1’, ‘the Low-Pressure Compressor 2 and 3’, ‘Normal Speed Enable’, ‘41MSpeed Enable’, ‘43M Speed Enable’, ‘45M Speed Enable’, and ‘VariableSpeed Enable’.

The low-pressure compressor motor outputs include four power relays. Twopower relays drive the low-pressure compressor 1 motor and the other twopower relays drive the low-pressure compressor 2 and 3 motors. Optoisolators drive the power relays. This is done to protect the CMOS logicfrom inductive spikes that occurs when switching the motors. When the‘Full On’ input goes high, one set of relays turns on, outputting 15 VDC(voltage of direct current) to all three low-pressure compressor motors102 a, 102 b and 102 c. When either or both of the second set relaysturn on, the variable voltage from the voltage regulators is outputtedto the appropriate motors.(See FIGS. 4M and 4N)

The pressure control 262 located on the control panel 200 is thevariable resistor that is inputted to the speed control board. It isbypassed when the variable pressure switch 290 is in the ‘CONST’position 290 a causing the mask port pressure to stay at 16 in H₂O.Otherwise the output pressure can be varied between 16 and 34 in H₂Owhen the test select switch 203 is set to ‘PBG’.

As part of preflight, the user verifies his or her communicationequipment. The user attaches to the tester and talks into themicrophone. The sound picked up by the microphone should be clearlyheard with the earphones. Audio system is made up of a preamp and apower amp. Several different kinds of microphones can be inputted intothe tester. There are four different microphone inputs. The primaryinput is ‘audio A’ 222. This input is configured to accept a 5-ohmdynamic microphone when the audio select switch 236 is in the LIS/TLK 1(listen/talk) 236 b. In the LIS/TLK 2 position 236 c, it is configuredto interface with an Electret microphone that requires 10-VDC (voltageof direct current) bias with 8 mA (milliamperes) current limit. In thisposition an audio input transformer and bias circuit is added to theinput circuit. The output of the audio input transformer is fed into thepreamp. There are two carbon microphone inputs parallel together. Thetwo inputs are the carbon headset jack 226 and the PTT (Press to talk)talk jack 228. These inputs 226 and 228 have 24-VDC bias current limitedto 10 mA. The input from the carbon microphone is fed directly to thepower amplifier bypassing the preamp. The primary audio output isthrough the audio A jack 222. In the LIS/TLK 1 236 b, it is setup tooutput into a 10-ohm dynamic microphone. In the LIS/TLK 2 position 236c, it is designed to output to 600 ohm input impedance earphones. The‘audio B’ jack 224 is always configured to accept 5 ohm dynamicmicrophone and output to a 10 ohm dynamic load. The audio A jack 222also provides +28 VDC (voltage of direct current) up to 200 mA power. Itcan be used to drive an ANR (Active Noised Reduction) unit.

A built in continuity tester can be provided to trouble shoot thecommunication gear. When the audio select switch 236 is in the ‘cont’(continuity) position 236 a, the communication circuits turn into acontinuity tester. The carbon microphone, dynamic microphone and dynamicheadset output DC resistance is monitored. If the dynamic microphoneinput resistance is between 4 to 7 ohms, the microphone light 230 willturn green. If it is less than 2 ohms, the microphone light 230 willturn red. If the output resistance is between 8 to 12 ohms, the earphonelight 232 will turn green. If the output resistance is less than 2 ohms,the earphone light 232 will turn red. If the carbon microphone inputresistance is between 80 to 500 ohms, the microphone light 230 will turngreen. If it is less than 20 ohms, the microphone light will turn red.The input/output resistance of these three circuits is determined byholding the current through input/output constant. Now the resistance isdirectly proportional to the voltage. This voltage is amplified and fedinto a window comparator and a limit comparator. The window comparatorscontrol the microphone/earphone green lights. If the comparators inputvoltage falls within the upper and lower set points, the green lightwill turn on. If the input voltage is less than limit comparator setvoltage, the red light will turn on.

To perform a goggle test, the EEU-2P flash goggles or equivalent areattached to the tester. After 10 seconds, the PTT button 228 is pressed.The goggles will turn opaque if they are working. 28 to 32 VDC issupplied to the EEU-2P goggles through the goggle jack 238. This voltagehas to be 27 VDC min (minimum voltage). when outputting 20 ma into 1400ohm. The shorted output current must be 70 mA minimum and not more than100 mA maximum. This is accomplished with voltage regulator and currentlimiting circuits.

FIG. 5 illustrates a general block diagram of a portion of the presentinvention. The diagram includes a gas system unit 802 which includeselements such as valve and compressor units and a speed control unit(See PCB3). The gas system unit 802 is controlled by the main PCB (PCB1)which uses the logic unit 804 to control the overall operation (See FIG.4). The logic unit 804 outputs control the speed control unit (SeePCB3), and the valves that control the flow. The communication unit 806is also included in the present invention and includes the audio unit808 (See PCB2) which is connected to PCB1.

The present invention integrates a plurality of testers into one unitand yet requires less power than earlier systems. The unit runs onstandard 115 or 230 VAC (voltage of alternating current), 47-440 Hz(hertz), 4 Amperes. Input requirements are 85-132/170-264 VAC 47-440 HZ(hertz) 400W (watts). The mask port pressure/flow output schedule isshown by the following table:

TABLE 1 Setting @ 0 LPM in H₂O @ 5.0 LPM in H₂O NORMAL 3.25 1.75 ± .541M 5.8 4.00 ± .5 43M 8.25 6.00 ± .5 45M 10.5 8.00 ± .5 PBG 16-32 NA LKHI 16-32 NA LK LO 16-32 NA

The tester 100 can be run from an internal rechargeable battery pack asan alternative to alternating current input from an outside sourceconnected to for example the battery port 250. The battery pack can benickel metal hydride batteries accessible through a weatherproof sidepanel. Other types of batteries such as lithium-ion and lithium-polymercan also be used. The power cord for outside power source can beattached to the back panel when the console is mounted. A built incharger can charge the tester in one hour or less or 20 minutes on theaverage. The tester can run up to 8 hours or more from its internalrechargeable battery pack. The duration can be increased depending onthe type and size of the battery.

The G-Suit port output pressure is shown by the following table:

TABLE 2 Setting Output Press. in H₂O G-suit on 58 ± 1 G-suit leak test0-150

An example specification of the present invention (CAST) is described asfollows.

The leak indication is shown by a leak above 5.5±0.5 lpm (liters perminute). The flow indication is 0-10,000±25 sccm and 0-300±1 sscm. Thepressure drop leak range is 0-5 lpm. The temperature limits for theoperating range is 0° C. to 50° C. while for storage is −40° C. to 75°C. The flash goggle power is 28+2 VDC (voltage of direct current),70-100 ma (milliamperes), current limited to 100 ma (milliamperes)maximum. The active noise reduction (ANR) power is +28±4 VDC (voltage ofdirect current) 200 ma (milliamperes) minimum. The microphone inputcurrent is 8 mA (milliamperes) maximum at 10 VDC (voltage of directcurrent).

With this configuration, the present invention can test all theaircrew's life support equipment. The present invention does not requireanything more than commonly available local power to operate. Thepresent invention is able to operate in a chemical warfare environment.The present invention does not require a separate high-pressure sourceof breathing air/oxygen. The present invention significantly reducessupporting man-hours, deployment costs and mobility footprint.

While the invention has been particularly shown and described withreference to the preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formand details may be made therein without departing from the spirit andscope of the invention.

What is claimed is:
 1. A gas system for testing aircrew systemsincluding a first system and a second system, said gas systemcomprising: an input filter located in an inlet port, said input filterfiltering an air to prevent foreign particles from entering said gassystem a first compressor compressing said air, said first compressorcomprising at least one blower, a speed of said blower depending on avoltage applied to said blower; a second compressor compressing saidair, said second compressor producing a lower flow at a higher pressurethan said first compressor; a first flow sensor detecting a flow of theair compressed by said first compressor and a leaking of the aircrewsystems; a second flow sensor detecting the flow of the air compressedby said first compressor and the leaking of the aircrew systems; a firstflow valve mounted for controlling the flow of the air compressed bysaid first compressor to said first flow sensor; a second flow valvemounted for controlling the flow of the air compressed by said firstcompressor to said second flow sensor; a regulator regulating a pressureof said second system; a first pressure sensor detecting a pressure ofsaid first system; a second pressure sensor detecting the pressure ofsaid second system; a first pressure valve for controlling the pressureof said first system; a second pressure valve for controlling thepressure of said second system; and a controller controlling anoperation of said gas system.
 2. The gas system of claim 1, with saidinlet filter designed to accept a chemical filter.
 3. The gas system ofclaim 1, wherein said first system is a mask, and said second system isa G-suit.
 4. The gas system of claim 3, said first compressor comprisingthree regenerative blowers connected in series, said three regenerativeblowers comprising a first blower, a second blower, and a third blower.5. The gas system of claim 4, each of said three regenerative blowershaving 21 inch H₂O of a maximum output pressure.
 6. The gas system ofclaim 4, said first compressor compressing the air for testing saidmask, said first compressor and said second compressor in ordercompressing the air for testing said G-suit.
 7. The gas system of claim6, said first compressor compressing the air until a G-suit pressurereaches a predetermined first pressure, said second compressor startingto compress the air when said G-suit pressure reaches said predeterminedfirst pressure and finishing when said G-suit pressure reaches apredetermined second pressure.
 8. The gas system of claim 7, whereinsaid predetermined first pressure is about 55 inch H₂O, and saidpredetermined second pressure is about 70 inch H₂O.
 9. The gas system ofclaim 3, further comprised of: said first flow sensor being able tomeasure the flow from 0 to 10,000 cubic centimeters per minute; and saidsecond flow sensor being able to measure the flow 0 to 300 cubiccentimeters per minute.
 10. The gas system of claim 3, furthercomprising: a first digital indicator reading out data outputted fromsaid first and second flow sensors.
 11. The gas system of claim 10,fixer comprised of: said first digital indicator converting the data toa digital signal presented as a number scaled in engineering units. 12.The gas system of claim 10, further comprising: a second digitalindicator reading out data outputted from said first pressure sensor;and a third digital indicator reading out data outputted from saidsecond pressure sensor.
 13. The gas system of claim 12, furthercomprised of said first limit valve being a solenoid valve.
 14. The gassystem of claim 3, further comprising: a first limit valve limiting thepressure of said first system.
 15. The gas system of claim 3, furthercomprised of said first flow valve, said second flow valve, said firstpressure valve, said second pressure valve being solenoid valves. 16.The gas system of claim 1, with said controller comprising a mainprinted circuit board (PCB).
 17. The gas system of claim 16, with saidcontroller further comprising a speed control printed circuit board(PCB), said speed control PCB controlling said first compressor bycontrolling a voltage applied to said first compressor.
 18. The gassystem of claim 16, with said main PCB using CMOS (complementary metaloxide semiconductor) logic.
 19. An apparatus for testing aircrewsystems, said apparatus comprising: a first unit testing a mask; asecond unit testing a g-suit; and a third unit testing communicationsystems, said first unit, said second unit, and said third unit beingintegrated, wherein said first unit and said second unit have a commongas system, said common gas system comprising a first compressor and asecond compressor, said second compressor producing a lower flow and ahigher pressure than said first compressor, said first compressorcompressing air when a pressure of an item to be tested is below apreset pressure value, and said second compressor compressing the airwhen the pressure of the item to be tested is equal to or over thepreset pressure value.
 20. The apparatus of claim 19, further comprisinga fourth unit testing a goggle.
 21. The apparatus of claim 19, furthercomprised of: said gas system comprising; an input filter located in aninlet port, said input filter filtering an air to prevent foreignparticles from entering said gas system; said first compressorcomprising at least one blower, a speed of said blower depending on avoltage applied to said blower; a second compressor compressing saidair; a first flow sensor detecting a flow of the compressed air and aleaking of the aircrew systems; a second flow sensor detecting the flowof the compressed air and the leaking of the the aircrew systems; afirst flow valve mounted for controlling the flow of the compressed airto said first flow sensor; a second flow valve mounted for controllingthe flow of the compressed air to said second flow sensor; a regulatorregulating a pressure of said G-suit; a first pressure sensor detectinga pressure of said mask; a second pressure sensor detecting the pressureof said G-suit; a first pressure valve for controlling the pressure ofsaid mask; a second pressure valve for controlling the pressure of saidG-suit; and a controller controlling an operation of said gas system.22. The apparatus of claim 21, with said inlet filter designed to accepta chemical filter.
 23. The apparatus of claim 21, said first compressorcomprising three regenerative blowers connected in series, said threeregenerative blowers comprising a first blower, a second blower, and athird blower.
 24. The apparatus of claim 21, said first compressorcompressing the air for testing said mask, said first compressorcompressing the air for said G-suit until a G-suit pressure reaches 55inch H₂O, said second compressor starting to compress the air for saidG-suit when said G-suit pressure is about 55 inch H₂O and finishing whensaid G-suit pressure is about 70 inch H₂O.
 25. The apparatus of claim24, further comprised of: said first flow sensor being able to measurethe flow from 0 to 10,000 cubic centimeters per minute; and said secondflow sensor being able to measure the flow 0 to 300 cubic centimetersper minute.
 26. The apparatus of claim 21, further comprising: a firstdigital indicator reading out data outputted from said first and secondflow sensors.
 27. The apparatus of claim 21, further comprising: asecond digital indicator reading out data outputted from said firstpressure sensor; and a third digital indicator reading out dataoutputted from said second pressure sensor.
 28. The apparatus of claim21, further comprising: a first limit valve limiting a pressure of saidfirst system.
 29. The apparatus of claim 28, further comprised of saidfirst limit valve being a solenoid valve.
 30. The apparatus of claim 21,further comprised of said first flow valve, said second flow valve, saidfirst pressure valve, and said second pressure valve being solenoidvalves.
 31. The apparatus of claim 21, with said controller beingincluded in a main printed circuit board.
 32. The apparatus of claim 31,further comprising a speed control unit, said speed control unit beingincluded in a speed control printed circuit board, said speed controlunit controlling said first compressor by controlling a voltage appliedto said first compressor.
 33. The apparatus of claim 31, with saidcontroller including CMOS (complementary metal oxide semiconductor)logic.
 34. The apparatus of claim 21, further comprised of: said thirdunit comprising an input accommodating a microphone, an inputaccommodating headset, and two inputs for carbon microphones.
 35. Theapparatus of claim 34, further comprising a built-in continuity tester.36. The apparatus of claim 34, with said third unit further comprisingan accommodation of a second headset and microphone accommodating afirst user to communicate with a second user.
 37. The apparatus of claim21, further comprising: a first limit valve limiting the pressure ofsaid mask.
 38. The apparatus of claim 37, further comprised of saidfirst flow valve, said second flow valve, said first pressure valve,said second pressure valve, and said first limit valve being solenoidvalves.
 39. The apparatus of claim 19, further comprising a controlpanel having a plurality of switches and indicators for controlling thetests for said first, second, third and fourth units.
 40. An apparatusfor testing aircrew systems, said apparatus comprising: a first unit fortesting a mask; a second unit for testing a G-suit; wherein said firstunit and said second unlit have a common gas system, said gas systemcomprising: an inlet filter for filtering an air to prevent foreignparticles from entering said gas system; a first system connected tosaid inlet filter, said first system comprising: a first compressorcomprising a plurality of blowers connected in series to compress saidair from said inlet filter; a flow sensor to detect a flow of said air;a first pressure sensor to detect a pressure of said mask; and a firstport through which the air flows to said mask; and a second systemconnected to said inlet filter, said second system comprising: saidfirst compressor and a second compressor to compress said air from saidinlet filter, wherein said second compressor produces a lower flow and ahigher pressure than said fist compressor, said first compressorcompressing air when a pressure of the G-suit is below a preset pressurevalue, and said second compressor compressing the air when the pressureof the G-suit is equal to or over the preset pressure value; a secondpressure sensor to detect the pressure of said G-suit; and a second portthrough which the air flows to said G-suit.
 41. The apparatus of claim40, further comprising a third unit for testing communication systems,wherein said first unit, said second unit, and third unit areintegrated.
 42. The apparatus of claim 41, further comprising a fourthunit for testing a goggle.
 43. The apparatus of claim 40, comprising:said flow sensor comprising a first flow sensor and a second flowsensor; a first flow valve mounted for controlling the flow of thecompressed air to said first flow sensor; a second flow valve mountedfor controlling the flow of the compressed air to said second flowsensor; a regulator regulating the pressure of said G-suit; a firstpressure valve for controlling the pressure of said mask; a secondpressure valve for controlling the pressure of said G-suit; and acontroller controlling an operation of said gas system.
 44. Theapparatus of claim 43, wherein said first flow sensor measures the flowfrom 0 to 10,000 cubic centimeters per minute and said second flowsensor measures the flow 0 to 300 cubic centimeters per minute.
 45. Theapparatus of claim 43, comprising: a first digital indicator reading outdata outputted from said first and second flow sensors; a second digitalindicator reading out data outputted from said first pressure sensor;and a third digital indicator reading out data outputted from saidsecond pressure sensor.
 46. The apparatus of claim 43, furthercomprising a speed control unit, said speed control unit being includedin a speed control printed circuit board, said speed control unitcontrolling said first compressor by controlling a voltage applied tosaid first compressor.
 47. The apparatus of claim 43, wherein saidcontroller includes a complementary metal oxide semiconductor logic. 48.The apparatus of claim 40, wherein said flow sensor is an electronicflow sensor.
 49. The apparatus of claim 40, wherein said first pressuresensor and said second pressure sensor are electronic pressure sensors.50. The apparatus of claim 40, wherein said filter is a chemical filter.51. An apparatus, comprising: a first unit accommodating a firstremovable test coupling to an appliance; a second unit accommodating asecond removable test coupling to a pressurizable garment; a gas systemcommon to operation of said first unit and said second unit, said gassystem having an intake port disposed to receive ambient air, said gassystem comprising: a first pressure sensor positioned to indicatepressure of the air at the first test coupling; a second pressure sensorpositioned to indicate pressure of the air at the second test coupling;a first compressor connected in series to said intake port to supply theair to said first test coupling and, when said second pressure sensorindicates that the pressure at the second test coupling is below apreset value, to supply the air to said second test coupling; a flowsensor positioned to indicate a flow of the air emanating from saidfirst compressor; and a second compressor connected to said intake portto supply the air to said second test coupling when said second pressuresensor indicates that the pressure at the second test coupling is equalto or greater than the preset value.
 52. An apparatus, constructed bysteps comprising: fitting a first unit accommodating a first removabletest coupling to an appliance; fitting a second unit accommodating asecond removable test coupling to a pressurizable garment; andincorporating a gas system in common to operation of said first unit andsaid second unit, said gas system having an intake port disposed toreceive ambient air, said gas system comprising: a first pressure sensorpositioned to indicate pressure of the air at the first test coupling; asecond pressure sensor positioned to indicate pressure of the air at thesecond test coupling; a first compressor connected in series to saidintake port to supply the air to said first test coupling and, when saidsecond pressure sensor indicates that the pressure at the second testcoupling is below a preset value, to supply the air to said second testcoupling; a flow sensor positioned to indicate a flow of the airemanating from said first compressor; and a second compressor connectedto said intake port to supply the air to said second test coupling whensaid second pressure sensor indicates that the pressure at the secondtest coupling is equal to or greater than the preset value.
 53. Aprocess of making an apparatus for testing an appliance and apressurizable garment, comprising the steps of: fitting a first unitaccommodating a first removable test coupling to an appliance; fitting asecond unit accommodating a second removable test coupling to apressurizable garment; and incorporating a gas system in common tooperation of said first unit and said second unit, said gas systemhaving an intake port disposed to receive ambient air, said gas systemcomprising: a first pressure sensor positioned to indicate pressure ofthe air at the first test coupling; a second pressure sensor positionedto indicate pressure of the air at the second test coupling; a firstcompressor connected in series to said intake port to supply the air tosaid first test coupling and, when said second pressure sensor indicatesthat the pressure at the second test coupling is below a preset value,to supply the air to said second test coupling; a flow sensor positionedto indicate a flow of the air emanating from said first compressor; anda second compressor connected to said intake port to supply the air tosaid second test coupling when said second pressure sensor indicatesthat the pressure at the second test coupling is equal to or greaterthan the preset value.